docs: def stop(self, nodes=None):
          """Stop one or many nodes.
  
          :param   nodes: Nodes to be stopped.
          :type    nodes: ``list``
          """
          if not self.is_connected():
              return None
  
          nodes = nodes or self.nodes
          result = []
  
          for node in nodes:
              if node.state == 'stopped':
                  logging.warning('Node %s is already "stopped".', node.name)
                  continue
              try:
                  status = self.gce.ex_stop_node(node)
                  if status:
                      result.append(node)
              except InvalidRequestError as err:
                  raise ComputeEngineManagerException(err)
  
          return result